In the pouring of concrete walls, such as for example foundation walls, what is typically done is to pour concrete footings on a suitable bed of gravel or the like. These footings extend upward to the level where the floor of the basement (or first storey, if there is no basement) will be. Two opposed forms are then erected which define between them a cavity into which concrete is poured. The forms are typically of metal or wood, and are of a standard size. Typically, the forms forming opposite faces of the cavity are joined together with pins (sometimes known as "ties") of metal or plastic. The ties are left in the concrete after it is poured, and form part of the wall.
Forms are typically supplied as a "system", which is a series of mating forms, often including forms of different sizes which are designed to be used with one another. There are a many systems in common use. They exhibit many different ways of joining the forms together edge to edge.
One of the most widely used systems of forms is composed of reusable plywood sheets of standard sizes, which are reinforced by having horizontal bands of metal reinforcement spaced at standard intervals and extending across their width on the face not intended to contact the concrete. For example, standard sheets of plywood for use in the system may be 8 feet in height, and 2 feet wide and of 11/4" thickness. The bands of metal are iron bands of about 3" inches in width and of the order of 1/8" to 1/4" thick. They extend parallel to the 2 foot dimension of the sheet at arbitrary distances from each other and the 2 foot long edges of the board, and extend the full width of the board, from one of the edges of a long side to the other edge of a long side. For example, commonly there are four bands, having their mid-lines at 8", 28", 52" and 76" respectively from the 2 foot edge which forms the bottom edge of the plywood sheet when it is assembled into a form,
Mounted on one end of each band, for example near the right edge of the face, is a pivotable hooking element, which pivots over and is retained by a post such as a large headed nail or screw or the like near the left edge of an adjacent like panel. Similar hook and post arrangements occur on the other bands, to hook adjacent panels together to make a form. The hooking element also has at least one (usually two) slots to fit over and retain in place iron ties extending to the similar forms making up the opposite wall of the cavity into which concrete is to be poured.
It is also known to build forms of blocks of plastic foam which define the cavity into which the concrete is poured. The foam is usually foamed polystyrene, although other types of foam plastic are sometimes used. The plastic foam can be left in place after the concrete is poured to function as insulation. Many form systems using foamed plastic are known. Representative ones are shown in U.S. Pat. No. 4,889,310 (Boeshart) and U.S. Pat. No. 5,140,794 (Miller). In the Miller patent, the forms are joined together by ties of wire. In the Boeshart patent, the ties are plastic.
Many systems use strengthening members, which are sometimes known as walers or wales, on the sides of the forms which do not contact the concrete. These may be horizontal or vertical, or both. Often, such walers are pieces of standard sized lumber, such as two-by-fours (lumber which is nominally 2" by 4" in cross section, although it is smaller after being dressed.) The forms or ties can be provided with members sized to hold walers of lumber. After the concrete has set, the walers are removed and the members which held them are removed in some way. In the Boeshart patent discussed above, the walers are held by an extension of the plastic tie, and the extension is removed by breaking it off. In U.S. Pat. No. 2,952,060 (Allen), the walers are held by brackets which attach to projections extending from the faces of plywood forms.
Most forming systems use either foamed plastic or plywood, but not both, to make their forms. U.S. Pat. No. 4,426,061, however, does show one embodiment where the forms on one side of the concrete cavity are of plywood and those on the other side are of foam. The patent is directed to a system which has tie members which interact with metal caps on the side edges of the foam panels. It also has metal channels in which the tie members rest. The system is a complicated one, with many parts which would be expensive to manufacture and keep in inventory. Additionally, the metal caps and metal channels provide passages for heat to travel around the foam panels, thereby greatly reducing the insulating effect of the foam panels.
Many contractors have a large investment in plywood forming panels. Such panels are reusable, and therefore tend to be cheaper than plastic foam panels, which stay in place and cannot be reused. However, the plastic panels do provide insulation value for the structure being built. There is therefore a need for a foam panel and tie system which is compatible with existing plywood systems, so that plywood can be used for forming which will be outside the building to be constructed and foam can be used for the forming to be inside the building to be constructed. Such a system should also be simple, with few parts to be kept in inventory.